/*
 * Copyright 1999-2009 The Apache Software Foundation.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.xml.security.utils.resolver.implementations;

import java.io.FileInputStream;

import org.apache.xml.utils.URI;
import org.apache.xml.security.signature.XMLSignatureInput;
import org.apache.xml.security.utils.resolver.ResourceResolverException;
import org.apache.xml.security.utils.resolver.ResourceResolverSpi;
import org.w3c.dom.Attr;

/**
 * A simple ResourceResolver for requests into the local filesystem.
 *
 * @author $Author$
 */
public class ResolverLocalFilesystem extends ResourceResolverSpi {

   /** {@link org.apache.commons.logging} logging facility */
    static org.apache.commons.logging.Log log = 
        org.apache.commons.logging.LogFactory.getLog(
                    ResolverLocalFilesystem.class.getName());

    public boolean engineIsThreadSafe() {
        return true;
    }

    /**
     * @inheritDoc
     */
    public XMLSignatureInput engineResolve(Attr uri, String BaseURI)
           throws ResourceResolverException {

        try {
            URI uriNew = getNewURI(uri.getNodeValue(), BaseURI);

            // if the URI contains a fragment, ignore it
            URI uriNewNoFrag = new URI(uriNew);

            uriNewNoFrag.setFragment(null);

            String fileName =
                ResolverLocalFilesystem
                .translateUriToFilename(uriNewNoFrag.toString());
            FileInputStream inputStream = new FileInputStream(fileName);
            XMLSignatureInput result = new XMLSignatureInput(inputStream);

            result.setSourceURI(uriNew.toString());

            return result;
        } catch (Exception e) {
            throw new ResourceResolverException("generic.EmptyMessage", e, uri,
                                            BaseURI);
        }
    }

    private static int FILE_URI_LENGTH="file:/".length();
    /**
     * Method translateUriToFilename
     *
     * @param uri
     * @return the string of the filename
     */
    private static String translateUriToFilename(String uri) {

        String subStr = uri.substring(FILE_URI_LENGTH);

        if (subStr.indexOf("%20") > -1) {
            int offset = 0;
            int index = 0;
            StringBuffer temp = new StringBuffer(subStr.length());
            do {
                index = subStr.indexOf("%20",offset);
                if (index == -1) {
                    temp.append(subStr.substring(offset));
                } else {
                    temp.append(subStr.substring(offset, index));
                    temp.append(' ');
                    offset = index + 3;
                }
            } while(index != -1);
            subStr = temp.toString();
        }

        if (subStr.charAt(1) == ':') {
      	    // we're running M$ Windows, so this works fine
            return subStr;
        }
        // we're running some UNIX, so we have to prepend a slash
        return "/" + subStr;
    }

    /**
     * @inheritDoc
     */
    public boolean engineCanResolve(Attr uri, String BaseURI) {
        if (uri == null) {
            return false;
        }

        String uriNodeValue = uri.getNodeValue();

        if (uriNodeValue.equals("") || (uriNodeValue.charAt(0)=='#') ||
	    uriNodeValue.startsWith("http:")) {
            return false;
        }

        try {
	    if (log.isDebugEnabled()) {
	        log.debug("I was asked whether I can resolve " + uriNodeValue);
            }

            if (uriNodeValue.startsWith("file:") ||
		BaseURI.startsWith("file:")) {
                if (log.isDebugEnabled()) {
	       	    log.debug("I state that I can resolve " + uriNodeValue);
                }
                return true;
            }
        } catch (Exception e) {}

        log.debug("But I can't");

        return false;
    }

    private static URI getNewURI(String uri, String BaseURI)
           throws URI.MalformedURIException {

        if (BaseURI == null || "".equals(BaseURI)) {
             return new URI(uri);
        }
        return new URI(new URI(BaseURI), uri);
    }
}
